Multilayer paper tape

ABSTRACT

A multilayer paper tape including two or more paper sheets which are bonded by adhesive layers is described. Each of the top layer and the bottom layer of this stack of paper sheets and adhesive layers is an adhesive layer, around which, as a casing, is formed a folded paper sheet enclosing the stack of paper sheets and adhesive layers. This folded paper sheet is completely surrounded by an adhesive layer. A process for producing the same is also described.

FIELD OF THE INVENTION

The present invention relates to a multilayer paper tape which can beused for forming a hooping of transport materials such as packages, pulpbales, pallets and so on.

BACKGROUND OF THE INVENTION

DE 197 21 683 A1 describes a packaging container to be used for forminga freight package made of a paperboard-cardboard material, the packagingcontainer being provided with a bonded, abrasion- and tear-resistanthooping for sealing and confining the packaging container, the hoopingbeing formed as a multilayered folded flat tape.

However, the hooping disclosed in DE 197 21 683 A1 proved not to havesufficient strength with concomitant good elasticity. Additionally, thehooping disclosed in DE 197 21 683 A1 does not have an antislipproperty.

SUMMARY OF THE INVENTION

An object of the present invention is thus to provide a biologicallydegradable hooping which has sufficient strength with concomitantacceptable elasticity and simultaneously provides sufficient antislipproperty for, on the one hand, preventing slipping of the hooping and,on the other hand, preventing slipping of the upper sheets in a stackedmaterial.

The subject matter of the present invention is a multilayer paper tape.

The subject matter of a further aspect of the present invention is aprocess for producing a multilayer paper tape.

The subject matter of the present invention is explained below in moredetail by an embodiment illustrated with the aid of drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a section of the multilayer paper tapeof the invention.

FIG. 2 shows an isolated view of a stack of paper sheets and adhesivelayers enclosed in a folded paper sheet.

FIG. 3 shows a pulp bale which is horizontally hooped by the multilayerpaper tape of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The multilayer paper tape of the invention preferably comprises two ormore, more preferably from 3 to 10, most preferably from 4 to 6 papersheets (2) which are bonded by adhesive layers (1) each provided betweentwo paper sheets. Each of the top and the bottom layer of this stack ofpaper sheets and adhesive layers is made of an adhesive layer. Aroundthese adhesive layers a folded paper sheet (3) is formed, as a casing,enclosing the stack of paper sheets and adhesive layers. The sheet edge(4) of the paper sheet which functions as a casing is hereby usuallyarranged so that it runs in the longitudinal direction of the papersheet (direction A in FIG. 1) on the upper or lower side (which is thebroad side) of the paper tape, preferably in the center on the upper orlower side of the paper tape (see for example FIG. 1. Additionally, theformation of a paper sheet casing into which a plurality of paper sheetsis inserted, may have one or more groups, preferably two or more groupsof compactions (6) and/or perforations (5). These can be formed on theupper and/or lower side of the paper tape. The compactions (6) areusually incorporated into the paper tape of the invention to improve therigidity of the paper tape of the invention. Surprisingly, it has beenfound that by incorporating perforations, the elasticity characteristicsof the paper tape of the invention can be enhanced. The compactions (6)and/or perforations (5) can run parallel to the sheet edge of the papertape of the invention or in a certain angle to it for the entire lengthof the paper tape or for only some sections of the paper tape.Preferably, the compactions (6) and/or perforations (5) are providedalong the entire length of the paper tape. In a preferred embodiment ofthe present invention the paper tape of the invention has two groups ofperforations running parallel to one another in the longitudinaldirection, wherein the two groups of perforations are displaced to oneanother in the transverse direction. If perforations running in thelongitudinal direction (direction A) are incorporated into the papertape of the invention, the elasticity of the paper tape of the inventioncan be increased. Thus, for example, by incorporating two groups ofperforations of from 0.2 to 2 cm in length, which are spaced apart fromone another by from 0.5 to 3 cm, preferably 0.8 to 2 cm in thelongitudinal direction and from 1 to 8 mm, preferably 3 to 6 mm in thetransverse direction, wherein the two groups of perforations aredisplaced to one another in the transverse direction, an elasticity isachieved which is improved by 100% (i.e., an increase of the elasticityof the paper tape of the invention from 4% to 8%). The compactions (6)are usually incorporated into the paper tape with an embossing devicesuch as a marking wheel and/or an embossing wheel. The perforations (5)are usually incorporated into the paper tape by means of a perforatingdevice such as a perforation wheel. The depth of the compactions (6) isusually from 0.01 to 1.4 mm, preferably from 0.1 to 0.4 mm. Thedistances of the compactions (6) in the transverse direction are usuallyfrom 0.1 to 5 mm, preferably from 2 to 4 mm. The distances of theperforations (5) in the longitudinal direction (direction A in FIG. 1)are usually from 0.5 to 3 cm, preferably from 0.8 to 2 cm, and in thetransverse direction (direction B in FIG. 1) usually from 1 to 8 mm,preferably from 3 to 6 mm. The perforations may be point perforations orperforations extending in one direction, for example in longitudinaldirection, having, for example, a length of from 0.2 to 2 cm, preferablya length of from 0.5 to 1.5 cm. The formation of the folded paper sheetoptionally having compactions and/or perforations into which is inserteda plurality of paper sheets, is integrally surrounded by an adhesivelayer to form a closed outer skin.

The adhesives used are, for example, a glue or a vinyl acetate adhesive,particulary a vinyl acetate adhesive.

The paper sheets have preferably a width between 1 and 100 mm, morepreferably 5 to 50 mm, most preferably 10 to 30 mm.

The thickness of the paper sheets is preferably 20 to 800 μm, morepreferably 100 to 500 μm, most preferably 200 to 300 μm.

The thickness of the adhesive layers is preferably 5 to 100 μm, morepreferably 10 to 60 μm, most preferably 30 to 50 μm.

The overall thickness of the multilayer paper tape of the invention ispreferably 0.01 to 5 mm, more preferably 0.1 to 2 mm, most preferably1.0 to 1.5 mm.

The paper sheet used according to the invention is preferably made fromwood pulp, semi-chemical pulp or chemical pulp, more preferablylong-fiber pulp.

By the presence of an adhesive layer as an outer skin of the paper tapeof the invention, the paper tape of the invention is provided with anantislip property so that the paper tape of the invention can also beused for horizontally bundling articles (see for example FIG. 3).Additionally, the antislip property of the paper tape of the inventionalso positively affects transportation because, by using the paper tapeof the invention, damage by transport machines can be prevented, such asby roller conveyor tracks or by forks of a high-lift truck.

The subject matter of a further aspect of the present invention is aprocess for producing a paper tape of the invention, comprising thefollowing steps:

-   -   bonding individual paper sheets by means of an adhesive into a        multilayer stack of paper sheets, each of the top and the bottom        layer being an adhesive layer;    -   folding a paper sheet around the stack of paper sheets; and    -   forming an adhesive layer in the form of a closed outer skin on        the stack of paper sheets having folded around a paper sheet.

In a preferred embodiment the process for producing a paper tape of theinvention comprises the additional step of compacting and/or perforatingthe paper tape obtained in step 2 above.

As explained above, the paper sheet used according to the invention isusually made from wood pulp, semi-chemical pulp or chemical pulp. Fromthese materials, webs of a suitable width, for example a width of from 5to 50 mm, are cut. Then the “bobbins”, as they are called, are usuallyprovided with an adhesive, superimposed on one another and compressed.As explained above, usually two or more paper sheets are arranged one ontop of the other. The superimposing of the paper sheets can, forexample, be made by using a commercially available tape productionapparatus. The resulting formation has an adhesive layer as each of thetop and the bottom layers. Subsequently, a paper sheet of an appropriatesize is folded around this stack of paper sheets followed bycompression. Then the resulting formation can be compacted andperforated, for example by means of an embossing or marking wheel and/orby means of a perforation wheel. Subsequently, the resulting formationis coated by an outer skin formed of adhesive. The coating can beperformed by an immersion treatment, for example. Subsequently the outeradhesive layer is dried and cured, for example, by using radiantheaters. By subsequently cooling the surface layer, the outer skin canbe prevented from cohering when winding up the multilayer paper tape.

Hereinafter, the present invention is described by way of an example.This example serves merely as an illustration in no way limits themultilayer paper tape as defined in the claims.

For producing the multilayer paper tape described in the presentexample, commercially available long-fiber pulp (brown paper of a basisweight of 160 g/m²) was used as a starting material. Then, from webs ofthis long-fiber pulp strips having a width of 19 mm and 39 cm,respectively, were cut in a roll cutter. These “bobbins” as they arecalled, were hung into the unroll gate of a commercially availabledraught frame and introduced one after the other into the draught frame.In the example described, 4 tapes of 19 mm in width and one tape of 39mm in width were used as a fold. All these paper tapes were guided overa plurality of deflection units through glue coating stations filledwith a commercially available glue (Türmer DL 100), followed bypositioning one above the other, compressed together and laying theprotective outer sheet around the stack of paper by means of a folder.Then two longitudinal compactions and two groups of longitudinalperforations were provided onto the tape by means of a marking wheel anda perforation wheel, respectively, so that the two groups ofperforations run parallel to one another in the longitudinal directionand run displaced to one another in the transverse direction (length ofperforations: 1 cm, distance in the longitudinal direction: 1 cm,distance in the transverse direction: 5 mm, depth of compactions on thetop and bottom side: 0.2 mm). Subsequently, the paper tape was onceagain drawn through a glue coating station to produce an antislip outerlayer. In order to strengthen and keep the form of the complete papertape formation, the resulting multilayer paper tape was then fixed anddried by means of radiant heaters (medium frequency infrared carbonradiators). The following cooling in a dancer-controlled cooling gateprevented the antislip outer skin from cohering when winding it up ontoa predefined cardboard core.

1. Multilayer paper tape comprising at least two paper sheets which arebonded together by adhesive layers to provide a multilayer stack,wherein each of a top layer and a bottom layer of the stack of saidpaper sheets and said adhesive layers is one of said adhesive layers,around which, a folded paper sheet is provided as a casing enclosing thestack of said paper sheets and said adhesive layers, said folded papersheet being completely surrounded by an adhesive.
 2. The multilayerpaper tape according to claim 1, wherein said tape has a total thicknessof from 1.0 to 1.5 mm.
 3. The multilayer paper tape according to claim1, comprising from 4 to 6 paper sheets.
 4. The multilayer paper tapeaccording to claim 2, comprising from 4 to 6 paper sheets.
 5. Themultilayer paper tape according to claim 1, wherein layer thickness ofthe paper sheets is in a range of from 200 to 300 μm.
 6. The multilayerpaper tape according to claim 1, wherein the folded paper sheet hascompactions, perforations, or compactions and perforations present in anupper side, a lower side, or upper and lower sides thereof.
 7. Processfor producing a multilayer paper tape according to claim 1 comprising:bonding individual sheets of said at least two paper sheets by anadhesive to provide said multilayer stack of said paper sheets and saidadhesive layers, wherein each of the top layer and the bottom layer ofthe stack is an adhesive layer; folding a paper sheet around the stack;and forming a closed outer skin of adhesive on the folded paper sheetpresent around said stack.
 8. The process for producing a multilayerpaper tape according to claim 7 further comprising providing in saidfolded paper sheet before or after said folding around said stack,compactions, perforations, or compactions and perforations on at leastone side thereof.